Rhodocybe griseoaurantia K.N.A. Raj & Manim.

MycoBank: MB 816843; Facesoffungi number: FoF02181

Etymology: The specific epithet refers to the greyishorange colour of the pileus.
Holotype: CAL 1324.
Basidiocarp small. Pileus 14 mm diam., convex with a slightly raised centre; surface greyish-orange (6B6/ OAC694) at the centre and pale orange (6A3/OAC695) toward the margin, hygrophanous and soon becoming orange-white (6A2/OAC696) after collection, not striate, finely appressed squamulose on and around the centre and minutely pubescent towards the margins; margin slightly incurved, rather wavy. Lamellae adnate to short decurrent, close, pale orange (6A3/ OAC695), up to 3.5 mm wide, occasionally furcate, with lamellulae of 1–4 lengths; edge entire or finely torn, concolourous with the sides. Stipe 31 x 4 mm, central, terete, slightly tapering towards the apex, solid; surface orange-white (6A2/OAC696), finely appressed-fibrillose all over, finely pruinose towards the apex; base slightly swollen, with whitish mycelial cords. Odour and taste not distinctive. Basidiospores 5–7 x 3.5–4.5 (5.85 ± 0.67 x 3.82 ± 0.33) um, Q = 1.25–2, Qm = 1.53; with 6–7 facets in polar view, ellipsoid in profile with or without a suprahilar depression, weakly undulate-pustulate all over, hyaline, thin-walled. Basidia 19–25 x 5–7 um, clavate, hyaline, thin-walled, 4-spored; sterigmata up to 3 um long. Lamella-edge often fertile or occasionally heterogeneous. Cheilocystidia 14–29 x 3–9 um, infrequent, scattered, often filiform or cylindrical, sometimes flexuous or narrowly fusiform. Pleurocystidia none. Lamellar trama subregular; hyphae 4–5.5 um wide, hyaline, thin-walled. Subhymenium inconspicuous. Pileus trama subregular; hyphae 3.5–8 um wide, pale yellow, thin-walled. Pileipellis a cutis often disrupted by scattered or rarely clustered ascending hyphae; hyphae 2.5–6 um wide, with a pale yellow wall pigment and occasionally with faint, hyaline encrustations, thin- to slightly thick-walled. Stipitipellis a cutis occasionally disrupted by scattered or clustered flaring-out hyphae; hyphae 3.5–6 um wide, hyaline or pale yellow, thin-walled. Caulocystidia absent. Clamp connections not observed on any hyphae.

Habitat: on soil, among moss, solitary.

Material examined: INDIA, Kerala State, Wayanad District, Muthanga, Muthanga Wildlife Sanctuary, 6 September 2011, K. N. Anil Raj AR865 (CAL 1324, holotype).

Notes: Rhodocybe griseoaurantia is well characterized by its small basidiocarps with a greyish-orange pileus; adnate to short decurrent lamellae; ellipsoid basidiospores and filiform or cylindrical cheilocystidia are the diagnostic features of R. griseoaurantia. Owing to the centrally stipitate basidiocarp, presence of cheilocystidia and the absence of both pseudocystidia and clamp connections, R. griseoaurantia can be placed in the section Rufrobrunnea (Baroni 1981). Rhodocybe alutacea Singer, a North American species (Baroni 1981; Baroni and Horak 1994), is similar to the present species in having similar coloured basidiocarps, a similar looking pileus, narrow lamellae with similar type of attachment, a solid stipe, almost similar-sized basidiospores of similar shape, infrequent, scattered cheilocystidia, pileipellis with encrusted hyphae and non-encrusted hyphae of stipitipellis. However, R. alutacea has larger basidiocarps, an umbilicate pileus, basidiospores with more facets (7–9) in profile view, larger, septate cheilocystidia, presence of caulocystidia and a different habitat and geographical location. Comparison of the RPB2 (681 bp), ITS (733 bp) and nLSU (908 bp) sequence data derived from R. griseoaurantia with the nucleotide sequences of taxa available in GenBank suggests that the present species is different. In the BLASTn search using the RPB2 sequence, the closest hit was Rhodocybe truncata (GenBank EF421019; Identities = 616/659 (93 %)). For ITS sequence, the closest hit was an unidentified Rhodocybe species (Rhodocybe sp. 1 GMB 2014) (GenBank KP012803; Identities = 719/737 (98 %)) from Australia, followed by R. truncata (GenBank EF421110; Identities = 556/644 (86 %)). In the BLASTn search with the nLSU sequence, the closest hits was Rhodocybe gemina (GenBank DQ071715; Identities = 894/ 908 (98 %)). Rhodocybe truncata (Schaeff.) Singer, a European species, differs from the present one in almost all macro- and microscopic characters, although it has cheilocystidia and rather similar-sized (5–6.5 x 4–5 um) basidiospores (Baroni 1981). Rhodocybe gemina (Paulet) Kuyper & Noordel., another European species belonging to the section Rufrobrunnea, differs from the present species in having larger and differently-coloured basidiocarps, crowded lamellae, a perfumed odour, unpleasant taste, slightly larger and differently shaped basidiospores (5–7 x 4–5.5 um), and a cutis with transition to a trichoderm type of pileipellis (Noordeloos 1988). In the phylogram, R. griseoaurantia, R. truncata and R. gemina formed a strongly support clade. This clade received significant support (98 % BS) and within it R. griseoaurantia was found to be phylogenetically distinct from R. truncata and R. gemina.

RPB2-based phylogram generated from maximum likelihood analysis (RAxML) depicting the placement of Rhodocybe indica, R. luteobrunnea and R. griseoaurantia within the genus Rhodocybe. Values at nodes indicate bootstrap support. BS values C50 % are indicated above or below the nodes, new species are in blue bold. The tree is rooted with Tricholoma flavovirens (KC816997) and Catathelasma imperiale (KC816994)


Rhodocybe griseoaurantia (CAL 1324, holotype). A Basidiome in the field. Scale bar 10 mm (Photo by K.N. Anil Raj)


Rhodocybe griseoaurantia (CAL 1324, holotype). a Basidiospores. b Basidia. c Cheilocystidia. d Pileipellis. e Stipitipellis. Scale bar a–e = 10 um (Photos by K.N. Anil Raj)